Compiling alsa-lib with Buildroot: C preprocessor fails sanity check

Question

Trying to compile a Linux image for LPC3250 ARM using Buildroot. Stock settings, it compiles fine. I'm getting this error when I try to add alsa-lib and alsa-utils:

configure: error: in `/home/user/projects/buildroot/output/build/alsa-lib-1.0.26                                                                ':
configure: error: C preprocessor "/home/user/projects/buildroot/output/host/usr/                                                                bin/arm-buildroot-linux-uclibcgnueabi-cpp" fails sanity check
See `config.log' for more details

Excerpt of alsa-lib's config.log. It kinda sucks because half the error messages have been cut off for some reason:

    /home/user/projects/buildroot/output/host/usr/arm-buildroot-linux-uclibcgnueabi/sysroot/usr/include/features.h:219:5: error: #error It appears you have defined _FILE_OF$
In file included from /home/user/projects/buildroot/output/host/usr/arm-buildroot-linux-uclibcgnueabi/sysroot/usr/include/stdio.h:72,
                 from conftest.c:12:
/home/user/projects/buildroot/output/host/usr/arm-buildroot-linux-uclibcgnueabi/sysroot/usr/include/bits/uClibc_stdio.h:61:2: error: #error Sorry... uClibc was built wi$
In file included from conftest.c:12:
/home/user/projects/buildroot/output/host/usr/arm-buildroot-linux-uclibcgnueabi/sysroot/usr/include/stdio.h:83: error: expected '=', ',', ';', 'asm' or '__attribute__' $
In file included from conftest.c:12:
/home/user/projects/buildroot/output/host/usr/arm-buildroot-linux-uclibcgnueabi/sysroot/usr/include/stdio.h:721: error: expected declaration specifiers or '...' before $
/home/user/projects/buildroot/output/host/usr/arm-buildroot-linux-uclibcgnueabi/sysroot/usr/include/stdio.h:723: error: expected ';', ',' or ')' before '*' token

Similar question here says something about "unsetting" CPP and CPPFlags. Not sure where I would do this or check for it within the Buildroot environment. I'm not sure if this is even the same issue. I'm guessing its not related since in that other question it's talking about compiling GCC, which I'm not doing.

My #1 hunch right now is that I have to edit the configure file for lib-alsa. I'm just not sure what edits to make.

Edit: Did some aggressive Googling and came up with what I think is the full version of one of my errors: ...features.h:329:2: #error It appears you have defined _FILE_OFFSET_BITS=64. Unfortunately, uClibc was built without large file support enabled. Checked my uClibc config file and UCLIBC_HAS_LFS=y is present. ???

Answer 1

The root of the issue here is Buildroot is using the uClibc config file located at: output/toolchain/uClibc-0.9.33.2/.config

rather than toolchain/uClibc/uClibc-0.9.33.config as specified in the Buildroot configuration menu.

I ran make uclibc-menuconfig (which defaults to saving the configuration in .config) and selected General Library Settings->Large File Support and everything compiled just fine.

Answer 2

Well, output/toolchain/uClibc-0.9.33.2/.config is generated from toolchain/uClibc/uClibc-0.9.33.config when Buildroot configures and builds uClibc. So it doesn't make any sense to use output/toolchain/uClibc-0.9.33.2/.config as the uClibc configuration. You should leave the default of toolchain/uClibc/uClibc-0.9.33.config.

Regarding Large File Support, normally all the packages have a proper dependency on it. So if a package needs large file support, the package cannot be selected until you enable large file support in Buildroot. If it is not the case, then it is a bug, and the Buildroot community would be interested in having a bug report about this (which details the Buildroot version being, the Buildroot configuration file being used, and the build error that you get).

Now, if Large File support is indeed needed, you should enable it at the Buildroot level rather than at the uClibc level. If you enable it only at the uClibc level, then Buildroot will not now about this, and will not show you all the packages that have a dependency on large file support.

So, what you should do is enable the BR2_TOOLCHAIN_BUILDROOT_LARGEFILE configuration option in Buildroot, and then do a complete rebuild: make clean all.